The woolly lemurs, also known as avahis or woolly indris, are nine species of strepsirrhine primates in the genus Avahi. They are endemic to Madagascar, where they inhabit the eastern rainforests and the western dry deciduous forests of the island. Woolly lemurs are the smallest indriids, with a head-body length of , a tail length of , and an average weight of . The fur is short and flocky. The pelage can be gray-brown to reddish, with a long, rufous tail and a recognizable white stripe running up the dorsal surface of the thigh. The head is round with a short muzzle, and the ears are hidden by the fur. The generic name Avahi is derived from an eastern Malagasy name for woolly lemurs, and there are many other local names for the genus. Although they were once considered to be a single species, woolly lemurs have a complex taxonomic history, with most members of the taxon having been described in the 2000s.
Woolly lemurs are typically the only primates that are simultaneously nocturnal, folivorous, and monogamous, although some populations of the southern woolly lemur (Avahi meridionalis) are cathemeral. Woolly lemurs can be found in both humid and dry forests, where they spend their lives traveling between tree crowns using their vertical clinging and leaping method of locomotion. They are strictly herbivorous, with their diets being primarily composed of young leaves. As nocturnal folivores, they take long naps throughout the night and sleep through the day to digest their fibrous diet. Woolly lemurs live in groups of two to five individuals, which typically consist of a bonded breeding pair and their offspring. Groups sleep together during the day in tree forks, vine tangles, and dense tree crowns. Both sexes participate in the defense of their territories, with conflicts involving aggressive chasing and vocalizations. Although females are dominant over males, woolly lemurs exhibit low rates of agonism between pair-bonded partners.
All nine woolly lemur species are classified as threatened by the International Union for Conservation of Nature, with the Sambirano woolly lemur (A. unicolor) and Bemaraha woolly lemur (A. cleesei) being classified as critically endangered. Threats include widespread poaching and deforestation resulting in habitat loss and fragmentation. Poaching of woolly lemurs is often motivated by food insecurities among rural Malagasy communities due to a lack of livestock as alternative meat sources, while deforestation is usually caused by bush fires created for slash and burn agriculture. These dangers are present both within and outside of protected areas.
Etymology In Malagasy, woolly lemurs are known as , which means "white leg," in reference to the white patch of fur on the dorsal pelage of the thigh in all species. In eastern Madagascar, woolly lemurs are known as , which is an onomatopoeia derived from a vocalization produced by woolly lemurs. Woolly lemurs in eastern Madagascar are also known by the Sabaki-derived name , which could be related to , a Swahili name for the Zanzibar red colobus (Colobus kirkii) on Unguja, or , a generic name for birds. An alternative explanation for the name relates it to the Nyakyusa word for the kipunji (Rungwecebus kipunji). In western Madagascar, the western woolly lemur (Avahi occidentalis) is known as the , which may be related to the Malagasy word for a curved mark or sign, .Blench, Roger & Martin Walsh 2009. Faunal names in Malagasy: their etymologies and implications for the prehistory of the East African coast. The Bemaraha woolly lemur is called , which means "grandfather of sifakas," on account of its resemblance to lemurs of the genus Propithecus.
Evolutionary history The Indriidae and Lemuridae families diverged from the Cheirogaleidae and Lepilemuridae families together about 43 million years ago, and were separated from each other shortly thereafter. The ancestral lineage of Avahi split from the ancestor of Propithecus and Indri about 29 million years ago. Woolly lemurs are basal indriids, as their karyotypes closely resemble the most recent common ancestor of Indriidae, compared to extant sifakas and the indri (Indri indri). The last common ancestor of all lemurs was hypothesized by Yves Rumpler et al. to have a somatic number of 2n = 66. Extant western woolly lemurs have a somatic number of 2n = 70, wherein all but two autosomal chromosomes are acrocentric. The X chromosome is submetacentric, and the Y chromosome is acrocentric. The eastern woolly lemur differs from the western woolly lemur insofar as it underwent a Robertsonian translocation between der(14) and an ancestral lemuroid microchromosome resulting in chromosome 2, and a pericentric chromosomal inversion of the ancestral lemuroid chromosome 1, from which arose the eastern woolly lemur's chromosome 1.
Genetic variation exists within Peyrieras's woolly lemur (A. peyrierasi) such that Rambinintsoa Andriantompohavana et al. identified two "types" of the species. Runhua Lei et al. later found there to be three types that lived in sympatry in forest fragments near Ranomafana National Park. Lei et al. assigned two of the types to a species complex that is shared with the Betsileo woolly lemur (Avahi betsileo), with a third type potentially being a different species, although they suggested that larger data sets across different generations should be acquired before any conclusions could be drawn about the types' taxonomic relationships.
Further genetic variation within the genus was identified by Rumpler in a population of eastern woolly lemurs in the Maromizaha Forest with a heterozygotic karyotype featuring an additional Robertsonian translocation. He speculated that this was the result of hybridization with an as of yet undescribed subspecies of A. laniger, or that the species exhibits intraspecific chromosomal polymorphism. No species or subspecies other than the eastern woolly lemur have since been described in the Maromizaha Forest.
Taxonomic classification Nine species are currently recognized. The genus is divided into two clades that correspond with the western and eastern distributions of the taxa.
Family Indriidae Genus Indri: indris Genus Propithecus: sifakas Genus Avahi: woolly lemurs East coast subgroup Eastern woolly lemur, Avahi laniger Peyrieras's woolly lemur, Avahi peyrierasi Southern woolly lemur, Avahi meridionalis Ramanantsoavana's woolly lemur, Avahi ramanantsoavanai Betsileo woolly lemur, Avahi betsileo Moore's woolly lemur, Avahi mooreorum West coast subgroup Western woolly lemur, Avahi occidentalis Sambirano woolly lemur, Avahi unicolor Bemaraha woolly lemur, Avahi cleesei
Changes in taxonomy
The earliest verifiable account of a woolly lemur specimen was published in 1782 by Pierre Sonnerat in his memoir, , wherein he details an eastern woolly lemur specimen that he acquired from the Antongil Bay area. He named the specimen , which was the only known woolly lemur specimen in Europe for almost 50 years. Sonnerat's specimen may not have been the first recording of the animal; Henri Milne-Edwards and Alfred Grandidier believed that a that was mentioned by Étienne de Flacourt in 1661 was also a woolly lemur. Sonnerat's was not granted a binomial name until Johann Friedrich Gmelin published his 1788 description of the specimen as Lemur laniger in the posthumous 13th edition of Carl Linnaeus' Systema Naturae. Using Sonnerat's specimen, Johann Heinrich Friedrich Link then wrote of a Lemur brunneus in 1795, based on Gmelin's description. Étienne Geoffroy Saint-Hilaire removed the woolly lemur from the Lemur genus in 1796, and instead assigned it to Indri as Indri longicaudatus. Johann Karl Wilhelm Illiger subsequently described it as Lichanotus laniger in 1811, with Lichanotus being an alternative generic name to Indri and Lemur. Later authors, such as Jan van der Hoeven and Daniel Giraud Elliot, would mistakenly bestow priority on Lichanotus over Avahi on account of the former preceding the latter. This nomenclature was invalid, as Illiger's Lichanotus was coined to replace the generic name Indri, rather than to move the woolly lemur to a unique genus. The first author to validly describe the woolly lemur as a monotypic genus was Claude Jourdan in his 1834 description of Avahi. Jourdan's prior description of the animal, Microrhynchus, was invalidated on account of the name having already been used by Johann Carl Megerle in 1823. Jourdan used the skin and skull of Sonnerat's specimen as his holotype, and derived the generic name from the Malagasy term for the eastern woolly lemur: the onomatopoeic or , which imitate one of the animal's vocalizations. Subsequent generic names include Avahis as a correction of Jourdan's generic name, Habrocebus , Semnocebus , and Iropocus .
The first taxonomic acknowledgement of variation within Avahi was described by Ludwig Lorenz von Liburnau in 1898, when he distinguished an eastern Avahi laniger laniger subspecies from a novel western A. l. occidentalis subspecies. He based this new description on a western woolly lemur skull and skin collected near Betsako by Alfred Voeltzkow in 1892. Both of the holotypes for Lorenz's subspecies, one of which was Sonnerat's , were later lost from their museum collections in Paris and Vienna, and had to be substituted with neotypes. Lorenz's taxonomy was used by scholars throughout most of the 20th century, and would not become obsolete until 1990, when Rumpler et al. proposed elevating both A. l. laniger and A. l. occidentalis to specific statuses after modeling an infertile hybrid between the two taxa. A third Avahi species, the Sambirano woolly lemur, was described on account of morphological evidence published in 2000 by Urs Thalmann and . Thalmann and Geissmann described A. unicolor as constituting the northernmost of three discontinuous populations of western woolly lemurs, while also suggesting potential speciation between the central and southern populations. They revisited Avahi in 2005, when they described the southernmost population as the Bemaraha woolly lemur. The description was based on a released type individual from which the authors obtained hair samples, photographs, recorded vocalizations, and morphometric data. They named the species in honor of John Cleese for his contributions to lemur conservation.